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Biochemistry > Photosynthesis L10 > Flashcards

Photosynthesis L10 Flashcards

1
Q

what are animals

A

heterotrophic organisms

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2
Q

what do animals require

A

an input of energy and nutrients in order to function

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3
Q

how do animals get energy input

A

contained in food and much of an animal’s existence is taken up in the pursuit of food

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4
Q

can animals make their own energy

A

Animals can synthesise some organic molecules but cannot generate their own energy or most nutrients which are gained from eating food

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5
Q

what do food chains describe

A

interaction between animals which eat other animals but at the start of all food chains are plants

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6
Q

what are the primary producers

A

plants

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7
Q

what are the consumers

A

animals

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8
Q

why is photosynthesis important

A

arguably most important process that occurs on earth

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9
Q

what is the most fundamental to the existence of life on planet

A

plants have ability to synthesise their own “food” in form of large complex organic molecules from simple molecules

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10
Q

how do plants build biomass in their structure

A

complex carbon based molecules

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11
Q

where is the energy derived from for plants

A

energy to carry out these synthetic processes is derived from sunlight absorbed by plant tissues

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12
Q

examples of photosynthetic processes

A

flowering plants
algae
mosses

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13
Q

how is photosynthetically synthesised biomass accumulated

A

photosynthetic organisms capture carbon dioxide gas from the atmosphere, fix it into existing carbon-based molecules acquiring carbon - build new molecules

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14
Q

what do plants need to gain biomass

A

uptake of water and a few nutrients from the soil

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15
Q

what are plants like

A

autotrophic – self sufficient, make their own food, producers

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16
Q

what are animals dependant on

A

consuming organic carbon based molecules to drive metabolism, food

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17
Q

where does photosynthesis get energy from

A

electromagnetic radiation (light)

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18
Q

what is energy used for in photosynthesis

A

synthesise short term high energy molecules used to drive biosynthetic reactions - newly synthesised organic molecules that plant uses to grow

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19
Q

what are the short term high energy molecules

A

ATP

NADPH

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20
Q

what is the estimated biomass production in the world

A

100 petagrams (100 x 1015 g) of carbon per year about half in the ocean (mostly by algae/phytoplankton) and half on land

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21
Q

what is a major component of terrestrial biomass

A

wood

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22
Q

why is wood important

A

fuel source

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23
Q

what is wood composed of

A

basically cellulose and lignin (lignocellulose)

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24
Q

what is cellulose made of

A

many sugar

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25
Q

cellulose structure

A

beta glucose molecules in a straight chain

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26
Q

what are cellulose fibres made into

A

folded into microfibrils

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27
Q

what is the major component of plant cell wall

A

microfibrils

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28
Q

what are microfibrils function

A

keep plant together e.g. leaves

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29
Q

what makes up the plant cell wall

A

Cellulose
Lignin
Hemicellulose

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30
Q

what is the structure of hemicellulose

A

branched beta glucose chain, cross links and side chains

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31
Q

what is the structure of lignin

A

different sugars linked and cross linked in different ways

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32
Q

what do algae form

A

Algae form phytoplankton in oceans and fresh water

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33
Q

what do the green plant leaves do

A

intercept light radiation from the sun

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34
Q

what is the structure of the leaf from the surface

A 
Upper epidermis
Palisade parenchyma
Vascular bundles 
Spongy parenchyma 
Lower epidermis
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35
Q

Where is the air space in the leaf

A

Spongy parenchyma

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36
Q

Why is the air space in the leaf important

A

Photosynthesis takes up carbon dioxide and makes oxygen – need gas exchange
Through stomata, regulates air movement

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37
Q

Why are the vascular bundles important

A

Transport highway of the plant, where sugar being made by photosynthesis is taken up and distributed to plant

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38
Q

Where are the chloroplasts

A

mesophyll cells

Upper part of leaf – where most sunlight

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39
Q

Where are chloroplasts derived from

A

Cyanobacteria

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40
Q

What is an organelle

A

Anything in the cell that is enclosed by a separate membrane

41
Q

What is the function of the inner membranes

A

Separate specific entity from cytoplasm and provide a specific biochemical environment to carry out specific reaction e.g. photosynthesis

42
Q

how long are chloroplasts

A

about 10 μm

43
Q

What do the chloroplasts contain

A

starch granules

44
Q

What is the function of the starch granules in chloroplasts

A

Starch being produced by photosynthesis stored here initially

45
Q

Where does photosynthesis happen

A

Thylakoid of chloroplast

46
Q

What is the function of stroma

A

Provides biochemical environment to carry out certain reactions

47
Q

what does the stroma contain

A

e.g. enzymes, carriers, many molecules

48
Q

what is the most inefficient enzyme

A

RUBISCO

49
Q

what does RUBISCO enzyme catalyse

A

reaction of ribulose-biphosphate to two molecules of 3-phosphoglycerate
Reaction uses a carbon dioxide molecule

50
Q

what does the reaction of fixing carbon contain

A

complex with short-lived intermediate molecules

51
Q

why is the fixing carbon reaction a C3 photosynthesis

A

result is two molecules of

3-phosphoglycerate, each containing 3 atoms of carbon

52
Q

what is the main reaction of photosynthesis

A

Fixing carbon - Main reaction that fixes carbon dioxide gas occurs in stroma of chloroplast, involves combining molecule of carbon dioxide gas with a simple phosphorylated sugar, ribulose 1,5 biphosphate

53
Q

how does carbon dioxide reach chloroplasts

A

Plants must have a constant supply of carbon dioxide, taken up by the stomatal pores, diffuse into the leaf into cells then chloroplasts

54
Q

what is RUBISCO enzyme built of

A

two types of subunits, each distinct proteins encoded by two different genes

55
Q

what are the two RUBISCO enzyme subunits

A

small subunits (SSU) and large subunit (LSU)

56
Q

how many kilodaltons is a small subunit of RUBISCO

A

14kD

57
Q

how many kilodaltons is a large subunit of RUBISCO

A

55kD

58
Q

why are functional enzymes huge molecules

A

Functional enzyme there are 8SSU and 8 LSU

59
Q

how is large subunit active site need to be activated

A

magnesium ions
carbon dioxide
enzyme Rubisco activase

60
Q

what do magnesium ions do

A

store electrons

61
Q

how many active sites are there on each enzyme

A

8

62
Q

are all the active sites on an enzyme the same activation state

A

8 active sites on each enzyme can be in different states of activation

63
Q

when is RUBISCO activated

A

only activated in the light (only needed in photosynthesis)

64
Q

what does RUBISCO do

A

transfer 5 carbon into two 3 carbon sugars metabolised into triose phosphate: use energy and electrons
> ATP ADP
> NADPH NADP+ + Pi

65
Q

what does the calvin cycle regenerate

A

3 C into 5 C sugar

66
Q

what is the main product of calvin cycle

A

Triose phosphate

67
Q

what is triose phosphate used in

A

used in many ways can be exported from the chloroplast and used to make sucrose in cytosol

68
Q

what is sucrose in calvin cycle used for

A

main metabolised sugar cells use for energy and metabolism

69
Q

why is the calvin cycle important

A

Major synthesis pathway in many plants carrying out photosynthesis during day

70
Q

what is exported from the calvin cycle

A

Sugar will be exported from leaf cells into plants plumbing system (phloem) and moved around plant to where it’s needed for growth (source/sink)

71
Q

what can triose phosphate alternatively be made into

A

converted into fructose-6-phosphate which forms basis for making starch in chloroplast

72
Q

what is starch

A

a polymer of glucose

73
Q

what is starch made of

A

two slightly different glucose polymers

74
Q

what are the two glucose polymers in starch

A

amylopectin

amylose

75
Q

what do plants synthesis in day

A

Plants can synthesise starch

76
Q

what does starch synthesis make

A

large starch granules within chloroplasts so by sunset, leaf’s chloroplasts full of starch grains

77
Q

what is amylopectin

A

branched starch

78
Q

what is amylose

A

one strain of starch

79
Q

how does amylose and amylopectin differ

A

different chemical properties

80
Q

what is starch broken down into

A

starch synthesized during the day is degraded into glucose and maltose and can be exported out of the chloroplast into the cytosol so that at dawn, no starch remains

81
Q

what percentage of carbon exported during photosynthesis

A

Arabidopsis leaf about 40% of carbon assimilated during photosynthesis

82
Q

what happens to the carbon exported during photosynthesis

A

used immediately by plant in metabolism and exported to make sucrose and other molecules

83
Q

what and why is carbon stored as

A

stored in chloroplast as starch for use in night

84
Q

what is the rate starch reserves are used

A

Starch reserves at night occurs at linear rate, and almost all reserves used up at dawn when photosynthesis starts again

85
Q

what is vital for plant growth

A

Pattern of starch accumulation and breakdown during 24 hours is vital for normal growth of the plant

86
Q

why is starch degradation under precise control

A

Flexibility and subtlety of this control is illustrated when plants are subjected to an unexpected early night

87
Q

what is Erythrose 4- phosphate is used to initiate

A

complex biosynthetic pathway which gives rise to three amino acids, phenylalanine, tyrosine and tryptophan inside the chloroplast

88
Q

where does Shikimate pathway occurs

A

chloroplasts

89
Q

what Shikimate pathway starting point for

A

synthesis of many complex aromatic and alkaloid molecules including lignin

90
Q

if amino acids not made what happens to plants

A

Amino acids not made, can’t form proteins, enzymes, cell walls – so die

91
Q

what does chlorophyll absorb

A

two blue and red light wavelengths

92
Q

why does chlorophyll absorb green wavelengths

A

because it is green

93
Q

what causes a helium nucleus of slightly less mass

A

fusion of four protons in the sun results

94
Q

what happens to the mass lost

A

converted to heat and electromagnetic radiation energy via the equation e=mc^2

95
Q

what is the first step of light driven electron transport on thylakoid membrane

A

Light energy is captured by chlorophyll associated with two protein complexes in the photosystem II and photosystem I

96
Q

what is the second step of light driven electron transport on thylakoid membrane

A

Flow of electrons between photosystems = generation of a proton gradient across thylakoid membrane, used to make ATP via the ATP synthase complex

97
Q

what is the third step of light driven electron transport on thylakoid membrane

A

Electrons for this process come from water which is broken down using light energy into electrons, protons and oxygen gas

98
Q

what causes plants to grow slower

A

pattern of starch accumulation and breakdown during 24 hours disrupted environmental changes grow less well than normal plants in predictable conditions
carbon shortage at night leads to starvation symptoms and temporary slowing or growth stops

Biochemistry (13 decks)

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